1. Field of the Invention
The present invention relates to catheter assemblies, crimping accessories, prosthesis retaining accessories and methods of crimping prostheses onto a catheter and retaining the prostheses on a catheter during delivery to a desired body location. More specifically, the present invention provides for catheters, crimping accessories, and retaining accessories that simplify the process of crimping a prosthetic valve to a catheter.
2. Background
Recently, minimally invasive approaches have been developed to facilitate catheter-based implantation of valve prostheses on the beating heart, intending to obviate the need for the use of classical sternotomy and cardiopulmonary bypass. For example, French Patent Application No. 99 14462 illustrates a technique and a device for the ablation of a deficient heart valve by percutaneous route, with a peripheral valvular approach. International Application (PCT) Nos. WO 93/01768 and WO 97/28807, as well as U.S. Pat. No. 5,814,097 to Sterman et al., U.S. Pat. No. 5,370,685 to Stevens, and U.S. Pat. No. 5,545,214 to Stevens illustrate techniques that are not very invasive as well as instruments for implementation of these techniques.
With regard to the positioning of a replacement heart valve, attaching a valve on a support with a structure in the form of a wire or network of wires, forming a frame, has been proposed. This frame can be contracted radially in such a way that it can be introduced into the body of the patient percutaneously by means of a catheter, and it can be deployed so as to be radially expanded once it is positioned at the desired target site. U.S. Pat. No. 3,657,744 to Ersek discloses a cylindrical, frame-supported, tri-leaflet tissue heart valve that can be delivered through a portion of the vasculature using an elongate tool. The frame is mounted onto the expansion tool prior to delivery to the target location where the frame and valve are expanded into place.
Current techniques for delivering prosthetic heart valves via a catheter include a transapical approach for aortic valve replacement, typically involving the use of an introducer port, i.e., a large-bore overtube, of a trocar. A crimped, framed valve prosthesis reversibly coupled to a delivery catheter is transcatheterally advanced toward the native valve, where it is either forcefully deployed using a balloon catheter, or, alternatively, passively deployed using a self-expandable system. Accurate positioning of the replacement valve in the native annulus is critical to the success of the implantation.
In order to prepare such valve prostheses for implantation, the valve prosthesis can be initially provided in an expanded or uncrimped condition, then crimped or compressed around the catheter until it is as close to the diameter of the catheter as possible. Various methods and devices are available for crimping the valve onto the catheter, which may include hand-held devices or tabletop devices, for example. These crimping devices can initially provide an opening that is large enough to accommodate a valve in its expanded condition and positioned over a desired section of a catheter. This valve can then be compressed by reconfiguring the opening of the crimping device in some way to uniformly decrease the size of the opening until the valve is compressed to a desired size. However, crimping a prosthetic valve using known hand held or tabletop devices requires a user to assemble and position the crimping device over a separately acquired catheter, resulting in the possibility of user error. In addition, positioning a crimping device over a catheter assembly can be complicated, for example, where the catheter assembly has a distal tip with a diameter larger than the final crimped diameter of the valve. In such situations, the known crimping devices are difficult to position on and remove from the catheter body.
The present invention provides a catheter assembly and crimping accessories for crimping a valve onto the catheter assembly. Crimping accessories according to the present invention can be provided pre-loaded onto a catheter assembly, and can be easily removed from the catheter assembly after a prosthetic valve has been crimped onto the catheter assembly, particularly with reference to catheter assemblies with enlarged distal tips. The crimping accessories described herein can also be provided separately from a catheter assembly and later positioned over the catheter. The catheter assemblies and associated crimping accessories described herein simplify the process of crimping a prosthetic valve and improve the accuracy of positioning the prosthetic valve within a body channel.